The odds of rolling straight 18's for a D&D character using the 3d6 x 6 method is:
1 : 101,559,956,668,416
-OR- 1 in 102 Trillion.
Now, going to 2nd Ed rules, if you roll an 18 for Strength, you roll a percentile dice (2D10) for Exceptional Strength.
Therefore, getting a 18(100)/18/18/18/18/18 (Technically Perfect) character in one roll requires beating odds of:
1:10,155,995,666,841,600 or 1 in 10 Quadrillion.
Last I checked, winning the Ohio MegaMillions is only 1:175,711,536, or 1 in 176 Million.
This statistical analysis is brought to you by Boredom and
TheFerrett .